Page 250 - Chemistry ICSE Class X
P. 250
236 ICSE Chemistry – 10
Let us say it Again
Ammonia is present near decaying organic matter or near a toilet, where it is formed due to the bacterial decomposition
of urea present in urine. In combined form, it occurs as ammonium chloride and ammonium sulphate.
Ammonia can be obtained
by heating ammonium salts with a caustic alkali.
by the action of hot water on metal nitrides, such as magnesium nitride, aluminium nitride, etc.
Ammonia gas is highly soluble in water and lighter than air. So it is collected by the downward displacement of air.
Ammonia gas is dried by passing it over quicklime.
The dehydrating agent, such as conc. H SO , P O and anhydrous CaCl cannot be used for drying ammonia gas because
2 4 2 5 2
it reacts with these reagents.
An aqueous solution of ammonia can be prepared by dissolving it in water by using a funnel-attachment to prevent
back-suction.
Ammonia is manufactured by the direct reaction between nitrogen and hydrogen. This process is called Haber’s process.
N (g) + 3H (g) 2NH (g)
2
2
3
Ammonia gas is basic in nature. The basic nature of ammonia is due to the presence of a lone pair of electrons on the
N atom in its molecule ( : NH ).
3
Ammonia gas gives dense white fumes when a glass rod dipped in hydrochloric acid is brought near it.
Ammonia reduces metal oxides to the corresponding metal when passed over heated oxides.
When dry ammonia gas and oxygen gas are passed over heated (800°C) platinum gauze, it gets oxidised to nitric oxide
(NO). The reaction forms the basis of Ostwald’s process for the manufacture of nitric acid.
Ammonia is used
as a refrigerant
for manufacturing urea, artificial silk, sodium carbonate and many ammonium salts.
